This sounds more like a network related problem - "invalid data" usually indicates that the network traffic is probably running through a "smart proxy" at the mobile carrier which tries to optimize data for web viewing (but unfortunately sometimes damages SyncML data).

If ZYB supports secure https/SSL access (I'm not sure about that), this will help as proxy equipment cannot interfere with encrypted SSL data which guarantees that data is transferred unmodified between your phone and the ZYB server.